1. Technical Field
The present invention relates to liquid developers and image-forming apparatuses.
2. Related Art
Examples of methods for developing an electrostatic latent image formed on a latent image carrier using a developer include a method using a dry toner formed of a material containing a colorant, such as a pigment, and a binder resin in a dry process and a method using a liquid developer having toner dispersed in an electrically insulating liquid carrier (carrier liquid) (see, for example, JP-A-2009-53638).
The method using a dry toner is advantageous in terms of handling because it uses a solid toner, although it has problems such as the risk of an adverse effect of powder on, for example, the human body, contamination due to scattering of toner, and unevenness in toner dispersion. Another problem is that, because dry toner aggregate easily, it is difficult to sufficiently reduce the size of the toner, and it is therefore difficult to form a toner image with high resolution. In addition, the problems described above, resulting from the fact that a dry toner is in powder form, become more serious as the size of the toner is reduced.
On the other hand, the method using a liquid developer allows the use of toner finer than dry toner because the toner aggregate less easily in the liquid developer, and also allows the use of a binder resin having a lower melting point (lower softening temperature) than a resin material used for a dry toner. Thus, the method using a liquid developer provides superior reproducibility of fine-line images, superior tone reproducibility, and superior color reproducibility, and also serves as a superior method for high-speed image formation.
For liquid developers in the related art, however, it is difficult to provide sufficiently high dispersibility for toner in a carrier liquid because of a low affinity between the resin material used for the toner and the carrier liquid.